Another memory card problem...Help anyone...Pls?

I recently upgraded my PC by adding a 512MB PC3200 400MHz 184 Pin DIMM card to replace 2 x 128MB PC133U 333MHZ 164 Pin CL3. It added a considerable amount of speed to the system, but after a few minutes of use it showed me and “unspecific” error with Internet Explorer and the system restarted itself back up.

I removed the new stick out and re-installed the 2 x 128MB and the system works slower but without any crashes.

The 512MB works fine offline until I access the internet. It works for a little while then crashes.

My motherboard (BIOS U8668 Grand) accepts up to 2G of memory. 4 slots for the memory (2 x 184 Pins and 2 x 168 Pins). The processor is an Intel Pentium 4. Windows XP Pro is my OS.

Is the memory card too much for the system or am I missing something here?

Thank you in advance for your helpful replies.

 

Perhaps the memory has to be added in matched pairs.